Charles Bosquier, the strict headmaster of a prestigious French boarding school, is furious when his eldest son Philippe fails his English exam. Determined to improve his son's language skills, he arranges an exchange with a Scottish family, sending Philippe to England while welcoming their daughter Shirley into his home. However, Philippe has other plans for the summer and secretly sends his friend Michonnet in his place. When Bosquier discovers the deception and learns that Philippe and Shirley have run away together, he sets off on a frantic pursuit, leading to a series of hilarious misunderstandings and chaotic adventures.